1. Field of the Invention
The invention relates to a casting mold in which at least a surface of the casting mold which forms a cavity is covered with a carbon film, and a cast article produced using the casting mold.
2. Description of Related Art
A technology of casting a metal product using a casting mold makes it possible to manufacture a large quantity of products having a certain shape and a certain level of quality, and this technology is applied to production of cast articles made of various metal materials. In a casting process, a surface of the casting mold, which forms a cavity to be filled with molten metal, is generally coated with a mold release agent. Thus, when the formed product is taken out of the casting mold, the cast product or article is easily released from the casting mold. However, if the casting process is repeated, the metal material may seize or adhere to the casting mold, or it may become difficult for the cast article to be released from the casting mold.
For example, when an aluminum alloy, or the like, is cast by a die casting method, molten aluminum is charged into the cavity of the casting mold at a high speed and a high pressure. As a result, seizing of molten metal may occur at a portion of the casting mold which contacts with the molten aluminum, or the mold release resistance may become large when the cast article is taken out of the casting mold, whereby a part of the cast article may adhere to the casting mold.
In view of the above point, a casting mold has been proposed in which at least a surface of the casting mold, which forms a cavity, is covered with a carbon film comprised of nanocarbon, and the carbon film is coated with fullerenes (see, for example, Japanese Patent Application Publication No. 2010-036194 (JP 2010-036194 A)).
However, even in the case where the casting mold as described in JP 2010-036194 A is used, the pulling resistance of the casting mold is high, and a part′ of the cast article may adhere to the inside of the casting mold if the draft of the casting mold is small. In this case, it may be considered to increase the draft, but the increase of the draft may result in reduction of the degree of freedom for the shape of the cast article.